The present invention relates to navigation systems and more particularly to a navigation system having an improved system and method for determining current position utilizing map matching.
Current navigation systems include one or more sensors for propagating the position of a vehicle. A sensor for determining displacement, such as a wheel speed sensor, is used in conjunction with a sensor for determining heading, such as a gyro, to generate a series of position vectors. The position vectors generally include a displacement and a heading. The series of position vectors forms a "dead reckon" path of the vehicle.
Generally, by periodically determining the position vectors of the vehicle, the navigation system can dead reckon the current position of the vehicle by utilizing "map matching". The navigation system includes a database of road segments, including segment length and intersection points. After receiving each new position vector, the navigation system compares the shape of the dead reckon path to the shape of the road segments in the database. The navigation system determines the current position of the vehicle by comparing the shape of the dead reckon path with the road segments in the database. After each new position vector is received, the navigation system compares the shape of the dead reckon path to all the potential road segments on which the current vehicle may be.
Near a node, or intersection, the navigation system may have to compare the shape of the dead reckon path to numerous road segments after each new position vector is received. This reduces the efficiency and speed with which the navigation system can rule out road segments and determine the current position of the vehicle relative to the road segments in the database.